Focused and directed laser beams are commonly used for a variety of processes, such as drilling of blind, through and micro-vias, laser imaging, dicing of substrates and modification or customization of integrated circuits, drilling, cutting, and selective material removal and other complex machining and micro-machining operations involving materials such as metals, polymers, integrated circuits, substrates, ceramics and other materials. Such processes have become very complex, often involving the concurrent or sequential of use of single or multiple lasers or multiple types of lasers, such as visible, infra-red (IR) and ultraviolet (UV) lasers, in concurrent or sequential operations. In general, however, the general object of a laser system is to controllably and reliably direct, focus and concentrate the energy of one or more laser beans to converge each beam at a desired spot or to image an apertured area of a laser beam onto the surface of an object.
Two recurring problems of conventional laser systems of the prior art, however, directly affect the reliable and controllable “pointing” of a laser beam to a desired location. The first, which is illustrated in FIGS. 1A and 1B, is often referred to as “beam wobble”, also referred to as “pointing instability”, and is the radial deviation of the Beam Axis 10 of Laser Beam 12 from an Optimum Centerline 14 by a Deviation Angle θ. Pointing instability is essentially inherent in both the properties of a Laser 16 itself, and in the normal operations of a Laser 16, such as “pumping jitter”.
The second problem of the prior art is illustrated in FIGS. 2A and 2B and is often referred to as “thermal drift”, which again causes the Beam Axis 10 of Laser Beam 12 to drift from an Optimum Centerline 14. Thermal drift is generally regarded as due to changes in the parameters of the Laser 16 due to heating during operation, changes in power levels and changes in the operational environment of the Laser 16. It should be noted that, unlike “pointing instability” which results in an angular deviation of the Beam Axis 10 from the Optimum Centerline 14, “thermal drift” results in a linear radial drift of the Beam Axis 10 with respect to the Optimum Centerline 14. That is, the Beam Axis 10 of Laser Beam 12 remains parallel to the axis of Optimum Centerline 14, but drifts radially away from Optimum Centerline 14.
The present invention addresses these and other related problems of the prior art.